This invention relates to sliver knitting machines and more particularly to the production of intricate pattern effects in circular knit deep pile fabrics.
In a typical commercial installation, deep pile fabrics are manufactured on circular knitting machines equipped with carding means that take fibers from slivers, or other loosely bound fiber assemblies, and supply these fibers to the hook portions of the knitting needles. Body yarns also are supplied to the hook portions of the knitting needles, and as the needles are manipulated to draw the body yarns into interlocked loops, the pile fibers supplied by the carding means are bound in with the body yarn loops. The end portions of the fibers project from the body yarn loops to form a pile surface on the knitted fabric. Ordinarily, air jets are directed toward the hook portions of the needles so as to dispose the pile fibers on the inside surface of the circular knit fabric. After the knitting operation, the tubular fabric is slit longitudinally and subjected to suitable finishing treatments such as shearing and the like.
Various techniques for achieving pattern effects in these knitted pile fabrics have been used heretofore. Of particular interest is the technique disclosed in U.S. Pat. No. 3,413,823 to Beucus et al., wherein pile fibers of different characteristics are delivered to axially spaced surface portions of the doffer element of the fiber feeding and carding head at each feed station, and the knitting needles are selectively raised into contact with one or more of the doffer surface portions to pick up fibers of the characteristics required for achieving the desired pattern effect.
Although such apparatus is quite satisfactory for the production of many patterns, it is less than ideally suited to the production of patterns wherein there are long intervals between stitches incorporating fibers of a given color. In these instances, such problems as undesired fiber buildup in the fiber feeding and carding lines may develop due to a lack of correlation between the fiber input and fiber utilization. Additionally, the cam system of needle selection specifically disclosed in the Beucus et al U.S. Pat. No. 3,413,823 is best suited to the production of short "repeats" or pattern sections, rather than the more intricate, long "repeat", pattern effects such as pictorial representations and the like.
In Brandt et al U.S. Pat. No. 3,709,002 these problems were very materially reduced by providing automatic coordination of fiber supply and needle selections. Due, however, to the difficulty of programming some intricate fabrics and, in some pattern situations due to an inadequate response characteristic, the fiber delivering means, i.e. doffer may experience an excessive fiber build-up or an uneven fiber delivery and needles taking fibers therefrom may pick up an overload or may be starved or underloaded, causing undesirable unevenness and variations in the fabric stitches and the pile of the fabric.
In addition, merely controlling fiber delivery in the fiber supply area of the machine places a limitation upon pattern design. Although in general designs may be attained by replacement of variously colored fibers in the pile of the fabric, desirable design effects may be attainable by variations in pile density at selected areas of a single color pile fabric. Prior arrangements have seriously limited or precluded attainment of numerous and varied desirable pattern effects.
While it is well known, of course, that during machine set-up, the depth of penetration of the needles can be predetermined by the proper positioning of the doffer rolls relative to the reach of the needles, the set-up adjustments are only feasible while the machine is inactive and remains static during operation of the apparatus. Any attempt to effect adjustments of the doffers relative to the needles during operation of the apparatus would, in prior apparatus, involve extreme hazard not only to the apparatus such as liability of needle breakage, but also to manipulating personnel. Therefore, in prior apparatus any change in adjustment of the normally static adjustment has necessarily been carefully avoided. To the best of our knowledge and information, there has been no prior suggestion that regulation of the quantity of pile fibers transferred to the knitting needles from the fiber delivery or supply means could be effected at the needles or the point of take-off of fibers by the needles at the fiber delivery means while running.